The present invention relates generally to boat hulls. More particularly, the present invention relates to boat hulls capable of planing.
As used herein, a boat hull “planes” or is a “planing boat hull” if it is capable of at least partially skimming across a water surface when propelled in a range of its normal operating speeds. In other words, as the boat hull increases from rest to its maximum operating speed, it makes a transition so that part of the hull that was submerged at rest has instead been lifted higher and approximately parallel to the water's surface.
More formally, planing can be defined in terms of vertical displacement of a boat's center of gravity relative to its rest level, also referred to as “vertical center of gravity” or “VCOG”. The center of gravity's position at rest is determined solely by hull buoyancy. As a boat accelerates bowward, VCOG at first drops, in part because the hull loses buoyancy due to wave action and other forces. In the case of a planing boat with a relatively flat lower surface, further acceleration causes VCOG to rise because the lower surface provides lift from dynamic forces. In this approach, planing is defined as beginning at the speed at which VCOG has been restored to its rest level.
Various planing boat hulls have been proposed, including boat hulls for racing, military purposes, and sport boating. One characteristic of many such hulls is a “V-bottom hull”, in which a center section of the hull's lower surface has a V shape. Many variations of V-bottom hulls have been proposed.
U.S. Pat. No. 3,237,581 describes a boat hull with a V-shaped bottom that meets each topside at a hard chine. The bottom surface includes a series of vertically stepped generally horizontal planing surfaces connected by longitudinally running, substantially vertical risers that are substantially parallel to the center line. Each planing surface has less dead rise than the next inboard planing surface and more dead rise than the next outboard planing surface. At slow, displacement speed, water parts at the bow and flows along the bottom, but as speed is increased, the bow shape imparts dynamic lift to the hull and its non-vertical surfaces. As speed increases further, the inboard planing surfaces begin to support the weight of the boat without the full assistance of the outboard planing surfaces. At high speed the outboard planing surfaces may rise out of contact with the water, the boat being supported only on the more inboard planing surfaces, which direct the flow of water resulting from contact.
U.S. Pat. Nos. 4,128,072; 5,983,823; and 6,176,196 are examples of the wide variety of other boat hull techniques that have been proposed. In general, these techniques involve modifying a planing boat hull in some way to achieve a desired result. For example, the ratio of length to beam can be increased.
It would be advantageous to have improved boat hull techniques. More particularly, it would be advantageous to have boat hulls permitting improved fuel efficiency and offering better performance when driven at lower power.